Wet Ash Impoundment Closure

Industry: Utilities

Location: Midwest

For this 140-acre wet fly ash impoundment closure, ENTACT conducted a phased dewatering approach, planning water flow, drainage and regrading of the exposed fly ash according to site elevation. The challenging regrading process set an elevation that would ultimately direct the subgrade for the construction of a new spillway. This spillway allows stormwater to flow from the closed site to a nearby creek.

The overall scope of work for the project involved lowering the main dam, removing the saddle dam and constructing a new spillway for both dams; draining surface water via pumping and temporary drainage channels; regrading exposed fly ash; and installing a multilayered capping system composed of geomembrane, geosynthetics, protective cover soil and vegetation. At project completion, our team managed over 2.5 million cubic yards of ash and soil, lined and capped 136 acres, and pumped and managed more than 7 billion gallons of water.